<h3>{% if text is defined %} {{text}} {% endif %}</h3>
<br>
<form method="post">
    <input type="text" name="login" placeholder="Введите логин" required>
    <input type="password" name="password" placeholder="Введите пароль" required>
    <input type="submit" name="button" value="Войти">
</form>